The amplification and typing conditions for the 13 core CODIS loci and their forensic applicability were evaluated. These loci are CSF1PO, FGA, TH01, TPOX, vWA, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, and D21S11. Results were obtained using the multiplex STR systems AmpFlSTR® Profiler Plus™ and AmpFlSTR COfiler™ (Applied Biosystems, Foster City, CA), GenePrint™ PowerPlex™ (Promega Corporation, Madison, WI), and subsets of these kits. For detection of fluorescently labeled amplified products, the ABI Prism® 310 Genetic Analyzer, the ABI Prism 377 DNA Sequencer, the FMBIO® II Fluorescent Imaging Device, and the FluorImager™ were utilized. The following studies were conducted: (a) evaluation of PCR parameter ranges required for adequate performance in multiplex amplification of STR loci, (b) determination of the sensitivity of detection of the systems, (c) characterization of non-allelic PCR products, (d) evaluation of heterozygous peak intensities, (e) determination of the relative level of stutter per locus, (f) determination of stochastic PCR thresholds, (g) analysis of previously typed case samples, environmentally insulted samples, and body fluid samples deposited on various substrates, and (h) detection of components of mixed DNA samples. The data demonstrate that the commercially available multiplex kits can be used to amplify and type STR loci successfully from DNA derived from human biological specimens. There was no evidence of false positive or false negative results and no substantial evidence of preferential amplification within a locus. Although at times general balance among loci labeled with the same fluorophore was not observed, the results obtained were still valid and robust. Suggested criteria are provided for determining whether a sample is derived from a single source or from more than one contributor. These criteria entail the following: (a) the number of peaks at a locus, (b) the relative height of stutter products, and (c) peak height ratios. Stochastic threshold levels and the efficiency of non-templated nucleotide addition should be considered when evaluating the presence of mixtures or low quantity DNA samples. Guidelines, not standards, for interpretation should be developed to interpret STR profiles in cases, because there will be instances in which the standards may not apply. These instances include (a) a primer binding site variant for one allele at a given locus, (b) unusually high stutter product, (c) gene duplication, and (d) translocation.

Allele distributions for 13 tetrameric short tandem repeat (STR) loci, CSF1PO, FGA, TH01, TPOX, VWA, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, and D21S11, were determined in African American, United States Caucasian, Hispanic, Bahamian, Jamaican, and Trinidadian sample populations. There was little evidence for departures from Hardy-Weinberg expectations (HWE) in any of the populations. Based on the exact test, the loci that departed significantly from HWE are: D21S11 (p = 0.010, Bahamians); CSF1PO (p = 0.014, Trinidadians); TPOX (p = 0.011, Jamaicans and p = 0.035, U.S. Caucasians); and D16S539 (p = 0.043, Bahamians). After employing the Bonferroni correction for the number of loci analyzed (i.e., 13 loci per database), these observations are not likely to be significant. There is little evidence for association of alleles between the loci in these databases. The allelic frequency data are similar to other comparable data within the same major population group.

The mitochondrial DNA (mtDNA) control regions of 125 domestic dogs (Canis familiaris) encompassing 43 breeds, as well as one coyote and two wolves were sequenced and subsequently examined for sequence variation in an effort to construct a reference dog mtDNA data set for forensic analysis. Forty informative variable sites were identified that described 45 haplotypes, 29 of which were observed only once. Substantial variation was found both within and among breeds in the mtDNA derived from tissue, indicating that analysis of the mtDNA derived from dog hairs could be a valuable, discriminating piece of evidence in forensic investigations. The dog data set single nucleotide polymorphisms (SNPs) ranged from having one to six changes on a phylogenetic tree. On average, there were 1.9 character changes for each variable position on the tree. The most variable sites (with four or more changes each, listed from the most changes to the fewest) observed were 15,639 (L 5 6), 16,672 (L 5 5), 15,955 (L 5 4), 15,627 (L 5 3), 16,431 (L 5 3), and 16,439 (L 5 3). These sites were consistent with other reports on variable positions in the dog mtDNA genome. A total of 26 SNPs were chosen to best identify all major clusters in the domestic dog data set. The descriptive analyses revealed that this data set is similar to other published canine data sets and further demonstrates that this domestic dog data set is a useful resource for forensic applications. This reference data set has been compiled and validated against the published dog genetic literature with an aim to aid forensic investigations that seek to incorporate mtDNA sequences and SNPs from trace evidence such as dog hair.

We report a large compilation of the internal validations of the probabilistic genotyping software STRmix™. Thirty one laboratories contributed data resulting in 2825 mixtures comprising three to six donors and a wide range of multiplex, equipment, mixture proportions and templates. Previously reported trends in the LR were confirmed including less discriminatory LRs occurring both for donors and non-donors at low template (for the donor in question) and at high contributor number. We were unable to isolate an effect of allelic sharing. Any apparent effect appears to be largely confounded with increased contributor number.

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